The conscious mind acts as a filter for the sense perceptions. The physical senses pick up the vibratory patterns and pass them along to the brain through the nervous system, but we only perceive those elements to which the mind has attended at some level. Western psychology has done a lot of work in the last 100 years or so to explore the limits of perception and the interaction of the senses, the nerves and the brain with the conscious filtering process. Experiments using hypnosis show that enormous amounts of sensory data is actually captured and stored in excess of what the mind can identify or recall. Experiments to capture vibration in the skin and overcome limitations of the ear for deaf individuals show that the mind can understand sensory data that does not come through the normal sense-organ channels. Psychologists such as C.G. Jung explored subliminal and subconscious levels of awareness that capture vast amounts of data that we simply do not attend to in our normal waking consciousness. These and other examples point the way (although they do not capture the entire meaning) toward the explanation provided by the Kena Upanishad of the existence of a Sense behind the sense that may or may not use the physical sense organs, but nevertheless is able to experience the reality of the universal creation. The sense organs are limited. This greater Sense is unlimited since it is based on the unity of the entire manifestation and not on the action of a particular physical mechanism to capture, transmit and translate vibratory patterns of existence.
Sri Aurobindo observes: “We know now or we rediscover the truth that the conscious operation of mind is only a surface action. There is a much vaster and more potent subconscious mind which loses nothing of what the sense bring to it; it keeps all its wealth in an inexhaustible store of memory…. The surface mind may pay not attention, still the subconscious mind attends, receives, treasures up with an infallible accuracy.”
“The Upanishads declare that the Mind in us is infinite; it knows not only what has been seen but what has not been seen, not only what has been heard but what has not been heard, not only what has been discriminated by the thought but what has not been discriminated by the thought. Let us say, then, in the tongue of our modern knowledge that the surface man in us is limited by his physical experiences; he knows only what his nervous life in the body brings to his embodied mind; and even of those bringings he knows, he can retain and utilise only so much as his surface mind-sense attends to and consciously remembers; but there is a larger subliminal consciousness within him which is not thus limited. That consciousness senses what has not been sensed by the surface mind and its organs and knows what the surface mind has not learned by its acquisitive thought.”
Sri Aurobindo, The Upanishads, Kena Upanishad and analysis, pg. 102, 142-155